This invention relates generally to pollution reduction, and, more particularly, to the treatment of airborne combustion byproducts.
Air pollution is a major problem in our society. A major source of air pollution is incomplete oxidation of combustion materials in a firebox or combustion chamber. Internal combustion engines, as commonly used in automobiles, provide energy by burning fuel. The energy is highly desirable, but the pollution they produce is not. Likewise, wood burning stoves provide useful heat by burning wood, but incomplete combustion results in the emission of undesirable hydrocarbon and other emission byproducts in the exhaust that they produce. The exhaust stacks of garbage incinerators and coal fired power plants also produce considerable quantities of undesirable emissions.
When organic material is combusted, whether it be in a wood burning stove, a utility power generation plant, an industrial furnace, or an internal combustion engine, one of the unpleasant (and as yet unavoidable) byproducts of the combustion process is the release of suspended particulate matter or hydrocarbon (HC) emissions. HC emissions are the result of partially combusted organic material escaping the combustion chamber before it is completely oxidized to carbon dioxide and water. In the last decade, over 11,000,000 tons of HCs were emitted from combustion sources in the United States each year. Of that total, approximately 65% of the HC emissions were from transportation sources and over 25% were from residential and commercial combustion (i.e., wood burning appliances). If HCs are maintained in a thermal environment above their combustion temperature, then the HCs will be completely oxidized prior to expulsion from the combustion device and the release of HCs eliminated. An added benefit of complete oxidation of the HCs to carbon dioxide and water is that carbon monoxide (CO) would also be oxidized to carbon dioxide, thereby eliminating an additional undesirable emission. To date, no cost effective means of completely eliminating HC emissions has been developed.
In the prior art, a popular device for controlling automobile engine and wood burning appliance emissions is the catalytic converter. It connects to the exhaust pipe and forces the exhaust to pass through a chamber that contains special materials which induce a chemical reaction in the exhaust. One of the special materials acting as a catalyst is platinum, making catalytic converters somewhat expensive to produce. Palladium, rhodium, other rare metals and/or alloys of these metals are also used in the manufacture of catalytic converters. However, catalytic converters do not remove all of the pollutants, and there is demand for less polluting automobiles and, thus a novel exhaust treatment system.
There have also been afterburners which combust the unburned or partially burned carbon compounds in the exhaust of an automobile. These have not been popular primarily because of the large amount of energy required to heat the exhaust to the point of combustion.
This invention uses a counter current heat exchanger. Such heat exchangers are commonly used in industrial furnaces to transfer waste heat from exhaust gases to incoming combustion gases. For heat exchange theory and examples of heat exchangers see Holman, J. P., Heat Transfer (7th edition)., New York: McGraw-Hill, Inc., 1990. In most industrial settings there is a large energy input to the system from the furnace burners so heat exchange efficiency between the exhaust gases and combustion gases is not a high priority. In fact, in many applications the primary purpose of the heat exchanger is to cool the exhaust gases rather than preheat the combustion gases.
Accordingly, there is a need for energy efficient devices which can reduce air pollution.